1. Field of the Invention
The present invention relates to an arrangement for limiting the rotational movement or displacement of a swivel unit mounting a lamphead. More particularly, the invention is directed to a rotation limiting arrangement for controlling the rotational displacement of a lamphead employed in an exit sign or the like within predetermined angularly defined boundaries, so as to thereby prevent the lamphead from at least partially obscuring the legend of the exit sign.
2. Discussion of the Prior Art
Currently, in both industry and commerce, among other applications, lampheads are frequently arranged on combination exit signs and similar products in order to provide illumination for specific legends which are represented by the exit sign. In view of a recent Underwriters Laboratory (UL) interpretation of the newly promulgated 1998 NFPA code, lampheads are not allowed to rotate downwardly relative to their mounting on an exit sign so as to either fully or partially, cover or obscure the exit legend. Consequently, in order to prevent any potential rotational movement of the lamphead from blocking or obscuring from view the exit sign legend, it has been considered necessary to consider developing an arrangement or device which prevents a lamphead from rotating or pivoting downwardly beyond a specific rotational limit.
In essence, a lamphead of the type described herein is supported on a swivel unit consisting of two mutually rotatable mating swivel halves which are normally held together in face-to-face contact by means of an interconnecting screw member so as to be maintained in rotationally fixed positions relative to each other. Ordinarily, one of the swivel halves mounts the lamphead whereas the other swivel half which mates therewith normally includes a radially extending post portion of hollow-cylindrical cross-section, which may have a hexagonal nut fixed thereto at a distal end, and from which a screwthreaded stub shaft extends in a coaxial arrangement so as to be able to be mounted on a suitable fixture or panel, as may be required by the particular utilization of the lamphead device. The swivel unit half which mounts the lamphead is adapted to pivot relative to the swivel unit half mounting hollow post and stub shaft to a considerable rotational. This aspect, at times, may lead to the lamphead being inadvertently rotated downwardly so as to either fully or partially cover or obscure the exit legend of the exit sign.